Thanks for all the responses! Here's a picture of my actual stuff:

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I'm more leaning to the 25 now, I definitely don't want to be buying another bag a year or two for now if I start running...

I'm trying to decide between the 19 and 25. My usual days I'm carrying 2 laptops: 13" Macbook Pro for work and 13" Macbook Air for myself, both are the newer models so they're quite thin. I also have...